1. Department of Electron Devices & Circuits, University of Ulm, Albert‐Einstein‐Allee 45, 89081 Ulm, Germany
2. Air Force Research Laboratories, 202 Avionics Circle, Dayton, OH 43240, USA
3. Department of Semiconductor Epitaxy, Otto‐von‐Guericke University Magdeburg, Postfach 4120, 39016 Magdeburg, Germany